SEDL / STP / STP426-EB / STP41337S

Metallurgical Variables as Possible Factors Controlling Irradiation Response of Structural Steels

Hawthorne, J. R.
Head, Mechanical Metallurgy Section, Reactor Materials Branch, Metallurgy Div., U.S. Naval Research Laboratory, Washington, D.C.

Steele, L. E.
Head, Reactor Materials Branch, Metallurgy Div., U.S. Naval Research Laboratory, Washington, D.C.

Pages: 39    Published: Jan 1967

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Abstract

Experimental investigations for the isolation and assessment of metallurgical factors causing variable radiation embrittlement sensitivity of reactor structural steels have been undertaken, using both large-tonnage commercial heats and special laboratory heats of steel. Metallurgical variables being evaluated include the identity and quantity of major alloying elements and of residual elements, steel-making practice—both melting (refining) and heat treatment practice, microstructure, and gas content. Experimental results from the initial series of the exploratory screening studies are presented and discussed. The results demonstrate that the radiation sensitivity of a steel can be altered appreciably through heat treatment practices and that microstructure plays a dominant, if not most influential role, in radiation sensitivity development. A tempered martensite structure was noted to be generally less radiation sensitive than tempered upper bainite and ferrite structures. The data also indicate that vacuum melting and the minimization of residual element content yields a superior irradiation performance to steels produced by conventional open hearth melting. However, longterm stress relieving heat treatments were not found to alter the irradiation response of A302-B steel.